Photomask and photomask blank

Abstract

In a low reflection type photomask (hard mask) having a chromium masking film provided, through or without an intermediary low reflection layer, on a transparent substrate and further having a low reflection layer provided on the chromium layer, use is made of a composite layer containing chromium oxide and chromium nitride as the low reflection layer. The composite layer is substantially equal in etching speed to the chromium film, and the photomask obtained is free from image deterioration caused by protrusions such as visors, burrs, or fractures, as observed in the photomasks of the prior art using chromium oxide films, and also has excellent durability.

What is claimed is: 
     
       1. A photomask blank comprising a transparent substrate and a multi-layer masking film provided on the substrate, said multi-layer masking film comprising a layer of chromium and a composite layer of chromium oxide and chromium nitride laminated on said chromium layer. 
     
     
       2. A photomask blank according to claim 1, wherein another composite layer of chromium oxide and chromium nitride is interposed between the chromium layer and the transparent substrate. 
     
     
       3. A photomask blank according to claim 1, wherein the atomic ratio of Cr:N:O in the composite layer is in the range of 1:0.1-0.3:0.8-1.4. 
     
     
       4. A photomask blank according to claim 1, wherein the composite layer is formed by sputtering or vacuum evaporation using as source a sintered product of mixed powders of chromium oxide and chromium nitride. 
     
     
       5. A photomask blank according to claim 1, wherein the composite layer is formed by reactive vacuum evaporation or reactive sputtering using chromium as source in an atmosphere of mixed N 2  -O 2  gas. 
     
     
       6. A photomask blank according to claim 1, wherein the composite layer has a thickness in the range of from 200 to 500 A. 
     
     
       7. A photomask comprising a transparent substrate and a patternized multi-layer masking film provided on the substrate, said multi-layer masking film comprising a layer of chromium and a composite layer of chromium oxide and chromium nitride laminated on said chromium layer. 
     
     
       8. A photomask according to claim 7, wherein another composite layer of chromium oxide and chromium nitride is interposed between the chromium layer and the transparent substrate. 
     
     
       9. A photomask according to claim 7, wherein the atomic ratio of Cr:N:O in the composite layer is in the range of 1:0.1-0.3:0.8-1.4. 
     
     
       10. A photomask according to claim 7, wherein the multi-layer masking film has been patternized by etching.